<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        .box1 {
            width: 800px;
            height: 800px;
            margin-left: 100px;
            position: relative;
            background-color: yellow;
        }

        .box1 .child {
            width: 300px;
            height: 300px;
            background-color: #FF0000;
            border: 1px solid black;
            position: absolute;
            top: 100px;
            left: 100px;
            margin-left: -130px;
        }

    </style>
</head>
<body>
<div class="box1">
    <div class="child">

    </div>
</div>
</body>
</html>